The proposed studies will examine how prosodic marking of the given/new distinction interacts with lexical stress to facilitate or impede infants use of speech rhythm in identifying words. Languages vary in how these different influences on prosody interact; therefore, to begin to get a handle on the cross-linguistic generality of early language processing it is important to examine whether certain prosodic cues (e.g., given vs. new stress) are consistent across languages, and whether these cues interact with prosody that is language specific (e.g., word-initial vs. non-word-initial lexical stress). Four studies are proposed: 1) an acoustic analysis of the given/new stress present in English and Spanish infant-directed speech, 2) an extension of work (Morgan, 1996b) examining predominantly English-exposed infants segmentation biases, however examining these biases in predominantly Spanish-exposed infants, and 3/4) perceptual studies of the influence of naturally produced given/new and lexical stress on English- and Spanish-exposed infants speech segmentation abilities. The specific methodologies relevant to these perceptual studies are a word monitoring procedure and a noise-detection method introduced by Morgan (1996a) that are based on the conditioned head turning method traditionally used to study infant speech perception.